<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>删除</button>
    <ul>
        <li>熊大</li>
        <li>熊二</li>
        <li>光头强</li>
    </ul>
    <script>
        var ul = document.querySelector('ul');
        var btn = document.querySelector('button');
        // 删除元素  node.removeChild(child)
        btn.onclick = function() {
            if(ul.children.length == 0){
                this.disabled = true;
            } else {
                ul.removeChild(ul.children[0]);
            }
        }
    </script>
</body>
</html>